The present invention is directed generally to fluid control systems for gas turbine engines and more particularly to fuel heating systems.
Gas turbine engines operate during varied environmental conditions, including at temperatures below the freezing point of water. Additionally, it is possible for the fuel to absorb water under various conditions. Ice crystals therefore have a tendency to form in the fuel under certain conditions, particularly at high altitudes or before the engine is operating. The ice crystals can plug fuel lines and orifices in the fuel system, which may degrade performance of the gas turbine engine or even cause an engine stall. As such, gas turbine engines are equipped with systems for eliminating or removing ice particles from fuel lines. For example, last-chance screens are often provided just before the fuel pump to remove any ice crystals. The screens, however, must be periodically cleared to prevent blockage of fuel flow. It is, therefore, more desirable to eliminate ice crystals from the fuel system altogether. Typical ice removal systems comprise a heat exchanger that imparts heat to the fuel from engine oil used to cool bearings in the engine. However, such systems require time for the engine oil to heat up, thereby delaying the melting of any ice crystals. Further, at high altitude conditions the heat exchanger may not be able to extradite adequate heat from the engine oil to melt the ice. There is, therefore, a need for improved fuel heating systems.